This invention relates to cement dispersants. At work sites where cement compositions are used, it is important to be able to provide high fluidity to cement compositions, to reduce the drop in the provided fluidity with time ("the slump loss") and to obtain a sufficient early strength during the initial period of hardening such that the frames can be removed quickly and the work efficiency can be thereby improved. This invention relates to cement dispersants which can respond to such requirements.
Examples of prior art cement dispersant for providing fluidity to cement compositions include salts of high condensates of naphthalene sulfonic acid formaldehyde and melamine sulfonic acid formaldehyde, as well as water-soluble vinyl copolymers. Cement compositions prepared by using salts of high condensates of naphthalene sulfonic acid formaldehyde or melamine sulfonic acid formaldehyde, however, have the problem of a high slump loss. Those prepared by using water-soluble vinyl copolymers of the conventionally proposed kind (such as disclosed in Japanese Patent Publications Tokko 58-38380, 59-18338 and 5-11057 and U.S. Pat. Nos. 4,962,173, 5,087,648, 5,290,869 and 5,362,829) have smaller slump losses but there are problems wherein their setting times become longer and hence a sufficient early strength cannot be obtained during the early period of hardening. This problem is particularly significant with high-strength cement compositions with a limited water-to-cement ratio.